One of Haskell's strengths is immutable data structures. These structures make it easier to reason about code, simplify concurrency and parallelism, and in some cases can improve performance by allowing sharing. However, there are still classes of problems where mutable data structures can both be more convenient, and provide a performance boost. This library is meant to provide such structures in a performant, well tested way. It also provides a simple abstraction over such data structures via typeclasses. WWW: https://github.com/fpco/mutable-containers